When you warm up your engine, the coolant expands and builds pressure, then the radiator cap allows the excessive coolant at a given pressure to flow into the reservoir. When you turn off your engine, and the cooling system starts to cool down, then there is a vacuum drawn from the radiator and the coolant in the reservoir is sucked/drawn back up the line into the radiator.
Your pressure cap controls this function. If it's not happening, then you need to replace your radiator cap.........

I found a thick layer of sand at the bottom of my reservoir. Looks like the rumor of casting sand in the system may be true. I asked this question because I wondered if there was a chance of the sand being sucked back into the system. Apparently there is. Since I have '13+ purple coolant on hand, I'm going to do a drain and fill as well as wash out the reservoir.

If that is in fact sand from casting that could explain why many members here are complaining of the water pumps going bad. I'd probably do a fresh water flush and refill with the Chrysler spec coolant. Just make sure you properly bleed the cooling system and then check once a day when the engine is cold for a couple of days and get all the trapped air out.

That also makes me think an early oil change isn't a bad idea either on a new Pentastar [any new engine for that matter], contrary to leave it in for the full OCI school of thought. Opinions vary.

Thanks for the info! I found a thick layer of sand at the bottom of my reservoir. Looks like the rumor of casting sand in the system may be true. I asked this question because I wondered if there was a chance of the sand being sucked back into the system. Apparently there is. Since I have '13+ purple coolant on hand, I'm going to do a drain and fill as well as wash out the reservoir.

I read on some site while researching why my oat coolant is orange that Chrysler is putting some slow release stuff in coolant tank that eventually disolved into the violent over time to inhibit corrosion. Will try to find it a again.

My wife's '13 has the same amount of sand stuff in her resovoir. Mine is build date Nov '12 hers is Feb '13. I suspect this from the factory.

The consistency of this stuff is very very fine and grainy. It is everywhere, even the radiator caps had to be rinsed there was so much sand in it. I could see the sandy stuff pour out when I drained the radiator.

I will say my water pump did not squeek the day after I did this. I even heat soaked the engine, which is what usually causes the squeek to occur. It might be coincidence. Not sure.

Yes, this stuff is pricey I highly recommend finding a strainer or filter that you can pour drained coolant through, or an inline filter to run for a few hours.

You don't think the agitation from driving through bumps, etc, wont stir it up and back in?

Radiator fluid isn't moving that much in the bottle as compared to the radiator. Let the sand settle to the bottom of the bottle, as long as the return tube isn't sitting at the bottom with the sand, it should create a one way for the sand to come in and stay. At least it would get some of the sand out of the cooling system.

The suck-up tube can't be cut shorter. Take a look at it when you get a chance. The tube outside the reservoir only plugs into the reservoir, the tube itself does not actually go into the reservoir. Instead, it goes into the resovoir at a connection point below the water line but not at the very bottom. It's basically doing exactly what you're aiming for by asking if you should cut the tube, so that's good.

The good news is the sand seems to clump nicely at the bottom of the resovoir and build up over time so I don't think its easily getting sucked back up. As long as you dump the junk in the reservoir then you'll slowly get sand out of the system.

I plan on just changing out the radiator fluid a few times.... I admit though a visit to the dealer would be a good idea.

You can guys should try opening your radiator caps. Look under the radiator cap itself, as well as into the radiator. Is it grainy and sandy? That's what I saw.

I'd be willing to bet this "sand" is probably the cause of a lot of the water pump failures members are reporting. I sure hope its not in the oil sump too.

The water pump failures have been, bearing related failures. The bearings do not run in the coolant, but rather in the oil.
The issue with the sand caused from the block casting, has been plugging up heater cores. That has been the number one complaint.
Mine has also been manufactured in Feb 2013, but does not have any sand in it. So it must only apply to some.

Legit, I suggest that you take them back to your Dealer, because they should be responsible to clean them out for you, under warranty. Remember, you didn't create the issue, but rather, Chrysler/Jeep did.

The water pump failures have been, bearing related failures. The bearings do not run in the coolant, but rather in the oil.
The issue with the sand caused from the block casting, has been plugging up heater cores. That has been the number one complaint.
Mine has also been manufactured in Feb 2013, but does not have any sand in it. So it must only apply to some.

Legit, I suggest that you take them back to your Dealer, because they should be responsible to clean them out for you, under warranty. Remember, you didn't create the issue, but rather, Chrysler/Jeep did.

Usually they're sealed units and not part of the oiling system, but I'm really not sure if Chrysler is using something different. Either way sand in the coolant can wreck the bearings in the pump, [if its set up that way] and the impeller that circulates the water, given enough time. It sure can plug up the heater core too. The bottom line is sand doesn't belong in the cooling system. I wouldn't be one bit surprised if it is contributing to the failing pumps, along with the possibility of a batch of defective pumps.

Honestly for the cost of the coolant they use, I'd bring it back and let them flush it out on their dime. Just make sure they bleed and refill it properly, and the anti freeze/water mix is up to par.

Sand in the cooling system will not effect the water pump bearings. But it will play havoc on the Impellor and seal. Also the abrasives in time will cause damage to the radiator, radiator cap and heater core. It has been known, to plug up the coolant flow in the heater core.

If it was mine, then it would be the Dealers responsibility to flush it out and give me a extended warranty on the cooling system in it's entirety.

Sand in the cooling system will not effect the water pump bearings. But it will play havoc on the Impellor and seal. Also the abrasives in time will cause damage to the radiator, radiator cap and heater core. It has been known, to plug up the coolant flow in the heater core.

If it was mine, then it would be the Dealers responsibility to flush it out and give me a extended warranty on the cooling system in it's entirety.

This once again, shows lack of quality control from Chrysler/Jeep!

Damage to pump bearings or not it can't be good for the pump or any part of the cooling system. How do you think it got there? Why wouldn't it be in the oil system too, if the blocks are cast in sand, and they're doing a crappy clean up job [obviously]? I love Chrysler, Jeep and Ram trucks what's going on with their QC?

Damage to pump bearings or not it can't be good for the pump or any part of the cooling system. How do you think it got there? Why wouldn't it be in the oil system too, if the blocks are cast in sand, and they're doing a crappy clean up job [obviously]? I love Chrysler, Jeep and Ram trucks what's going on with their QC?

I think that they have a issue, as to when the block, and or cylinder heads were casted and then they were not cleaned properly, before assembly. Some of the sand casting particles have flaked off and still remained in the cooling ports.
As for the oil as a possibility, maybe? If I had the issue, then I would have a oil analysis run, just to see if they detect any. At least you have a oil filter to clean that portion of your block.

I changed my oil at 1000 miles and then 2500, and both times I looked at my oil filter pleats for particles, and didn't see anything. But mine doesn't have the issue in the cooling system either, so it's really not a good example.

I also think highly of the Jeep products, or I wouldn't have owned them for many years. But, they obviously do have some quality control challenges ahead of them.